Centralized traffic controlling system for railroads



Aug. 15, 1939 N. D. PRESTON CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS e sheets-sheet '1 Filed May 16, 1936 Allg. 15, 1939 N. D. PRESTON f 2,169,480

CEN'IVRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Filed May 1e, 195e e 'sheets-sheet 2 Aug. 15, 1939 N. D. PRESTON 6 Sheets-Sheet 5 Filed May 16, 1936 JT v: L1|. m +Mw .Us L.vw @Q www u |T|||||1l1 r||||| hHNHm- Lnn mlm r ...V I I L @l l.. 1| 11| V ...v E S v o? www Aug. 15, 1939 N. D. PRESTON 2,169,480

CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Filed May 16; 1936 6 Sheets-Sheet 4 Aug. 15, 1939 N. .I PRESTONv 2,169,480

CENTRALIZED TRAFFICCONTROLLING SYSTEM EOR RAILROADS Filed May 1G, 1936 6 Sheets-Sheet 5 -lLlLlLlllLlllkl aan. uz

Aug. 15, 1939. N Dl PRESTON 2,169,480

CENTRALIZED TRAFFIC CONTROLLING' SYSTEM FOR RAILROADS Filed May 16, 1936 6 Sheets-Sheet 6 EHETT un; mi

IllrllLlllrll 2i; will be understood that the invention is not For Convenience lriesrbiung the Operation Patented Aug.15,1939 d Y Y 2,169l480 UNITED STATES PATENT OFFICE CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Neil D. Preston, Rochester, N. Y., assignor to General Railway Signal Company, Rochester, N. Y.

' Application May 16, 1936, Serialr No. 80,095

8 Claims. (Cl. 177-353) This invention relates to centralized tra-flic character (polarity) as determined by the secontrolling systems for railroads and it pertains lectiverconnection of the A line to the S line more particularly to the communication part of `and the C line at the station. This selective such systems. connection provides a choice of two indications In railroad traffic controlling systems the traffor each step of the stepping mechanism. Adc is controlled from .a control oce usually .ditional indications are transmitted by selectively located at a central point with respect to an connecting the B line to the S line and the C outlying field station or a plurality of field staline at the station. This selective connection of tions. The eld station or stations are conthe B line circuit also provides a choice of two 1.o neeted to the control office by means of the comindication conditions for each step of the stepvl0 munioation system, The location of trains and .ping mechanism. Thus a choice of four lindicathe condition of the various traiiic Controlling tion conditions is provided on each step.

devices at the outlying field station or stations This selective energization of the A and B line are indicated toV the attendant in the control circuits is controlled at the field station from 'i5 oice. These indications relating to the condi- .energy Supplied by the CODIOl 4Office lIle battery. 15

tion of the tramo controlling devices and the like irrespective of the Apolarity With which the S line are transmitted to the control oii'ice by means of and -the C linek is energized asy selected at the the communication system. .control cnice. The :selective venergization of the The present invention is particularly useful in A and B line circuits is consequently determined a system which is called upon to carry out a re'lat the transmitting eld Steen 111 PIODeI CO- 20 atively large number of controls and indications relationWith the polarity of energization of the during a short time. The present embodiment Sand C line conductors at the control oince, all

'more particularly relates to a system comprising of which will be pointed out in the detailed dea control oice and a single station although it scription which follows.

limited to a single station. of this system the energized periods of the S line The communication lsystem provided interconf ircuit Will be referred to as the "011 periods and nects the-control ofce and the field station and the deenerglZed periods pf Vthe S lille oirCuitWll it is so organized that complete control and sube `conveniently referred to as the ofi periods. pervision of the various devices,such as the track In the first IIlOdifiCatiOil. ell line circuits are .3J switch and the signals therefor, are obtained .by normally Cleelelgzed- Al the Steril V0f e COIlifIOl the operator. Such a traflic controlling system Cycle the S line circuit is energized with .a (l-) is supplemented by the usual automatic block impulse .for conditioning the Circuits and after signal system and other local means ordinarily these circuits are properly conditioned the SYS- provided to guard against unsafe train moyetem Steps through an'operaiing eyele in a man- 35 ments, improper operation of track switches and ner which vwill be described in detail. When the the like. System is initiated from the field Vstation the A In accordance with the preferred form of the line Circuit iS energized LWith e (-1-) impulse fOr present invention (Figs, 1, 2 and 3) the comconditioning 'the circuits .of the system, after a() munication system comprises a four Wire line Which the SYStem Steps through e Cycle 0f 01)-, 40

circuit extending from the control office to the eratiolls as Will be explainedin detail. outlying field station. These four line Wires are ID aeeordenee With e mOdiCatOIl (Figs. 4, 5 referred to in this ydisclosure as the S line, the C and 6) use is made of Ya five wire line circuit, line, the A line and the B line. The S and the over which double lthe number of controls and i5 C lines form a circuit over Which stepping imindications (compared With the System 0f Figs. 45 pulses are transmitted and over which control l, 2 and 3) are transmitted. -The same fundaeede combinations are transmitted. The A and mental principle used in the Vsystem.already de- B line conductors are arranged to belselectively scribed, that is, 'the use 0f DOleIimDU-lSeS derived connected to the S and C line conductors for from a source of current in the control office for the transmission of indications. The C line conthe transmission of indications, is used in this ductor is therefore a common conductor for the modification. S line circuit and for the circuits made'up, in- The schematic circuit diagram of Fig. 4 indi- -cluding the A and B line conductors. catesthe live wire line circuits V.and the: appara- Ylor the transmission of indications,r the Aline tus most closely associated rwith these `line cir- 5 circuit is energized with mpulsesof distinctive cuits. l'The S line, in combination With the A 55 and B lines forming return paths for impulses A in the S line, is used for controlling the stepping operation and for transmitting a choice of two controls atY each step. The A line in combination with the B line as a return conductor is used for transmitting a choice of two additional controls for each step. vAs indicated in the control oiiice portion of this figure, line battery LB sup- `plies energy for the transmission of stepping impulses and one set of controls, the polarities of which are determined by the PC and NC re-V lays. The controls transmittedbver the A line vcircuit are made up of impulsesfrom the source of current 2LB, with the polaritydeterminedby relay PX. Y.

A choice vof four indications is provided during the oif periods by energizing Ythe MA and MB line circuits with polar impulsesy selected at theV neld station, the polarity of which is supplied from battery V2LB in the control oiiice being connected tothe A and B line conductors. YThese vfour vlfoffff indications are selected through back contacts ofl relay FP1 at the eld stationY as in- 'fsk Ydi'cate'd `by the legends to MAB (and to MBB) indication circuits selected by stepping relays. This refers toi the fact that the MA and MB lines are conditioned through back contacts of relay FP1V. `The back contacts of relay FP in the control oiiice connect to relays MAB and.

MBB, which reIaysare operated bythe polar vimpulses applied to the respective line circuits.

Y,During the on periods, when relays FP and 'FPi are picked'up, additional-'indicationY circuitsV are selected as indicated bythe legends which refer to thevMAF and MBF indication circuits.

The frontcontacts of relay FP inthe oflice lead through relays MAF and MBF so that these Vrelaysmay' be selectively operated in accordance with thepolar impulses applied to the MA and MBrlines respectively,VV f

`Other objects and Vadvantages of the present invention willbehereinafter set forth in the Ispecification and claims and further details will be understood by referring tolthe accompany 'ing drawings which illustrate the different meth- Yods kof carrying yout the invention by way of voftheir operation and in which:- f

example.

Fig.V 1 illustrates in a schematic ,arrangement of the line circuits, which connect the controlroice with the eld station, showing .TheV Vdrawings illustrate 'in .a diagrammatic manner the apparatus and circuits employed and Yfor convenience in describing the invention those partslwhich have similar features and functions are designated .in the different figures by like reference characters, generally made distinctive bythe use of distinctive exponents representative of their location and by the use of suitable preceding numerals representative of the order manner the only the apparatus most closely associated with Ythe linecircuits.

y' i Fig. 2 illustrates in more detail the apparatus Yand circuit arrangement employed Vat the control oijlice for providing means whereby an operator may govern the switches and signals at'the eld station and whereby indications may be received Yin the control oce fromV the iield station.

` Figj3 illustrates the apparatus and circuit arrangement of the preferred Vform somewhat in detail, as employed at the field station for 'pro- Vviding control of a single track switch'and 4for transmitting indications Atothe Ycontrol cnice in accordance with the'present invention. A

When tracing the' Ydetailed circuits vof the first Fig. 5 illustrates in more detail the apparatus and circuit arrangement (of the modification)V employed at the control office for providing *means whereby, an operator may govern the switchesA and signals at the field station and whereby indications may be received in the control oice fromV the Vfield station.

Fig.'6 illustrates the apparatus and circuit Y arrangement somewhat in detail (of the modication), as employed at the field station for providing Control of a single track switch and for transmitting indications tothe control office in accordance with the present invention.

When tracing the detailed circuits of the modificationFig. 6 should be placed to the right of, Fig. 5 with correspondingly numbered ylines in alinement. Y

' Forthe purpose of simplifying theY illustra? Y Vtions and facilitating inthe explanation, vari# ous parts and circuits have been diagrammatically shown and certain conventional illustra tions have been employed. The drawings have been made more with the purpose of making iteasy to understand the operation of the invention than 'with the idea, ofillustrating the specic vrconstruction and arrangement that would preferably Ybe employed in practice.

.,'Tlie'symbols and are', employed to indicatek thev positive and negative terminals respectively of suitable batteries'or other sources ofV current and the circuits with which these symbols are used have'current iiowing in the The` same. direction, that is, from to symbols (B+) Vand (B-) are employed to indicate the positive and negative terminals respec-Y` tively of a suitable battery or other sourcerof Vcurrenthaving a Vmid-tap (CN) andthe circuits with which these symbols are used may have Vcurrentflowing in one direction or the other depending upon whether the Vterminal (B+) or (BJ- is used in combination with tap V(CN). Y Control ofice equipment, preferred form- The control oiiice (see Fig. 2) includes a control machine having a group of control levers associated `with the field station, va miniature track layout corresponding to thetrack layout at the station vand' various indicating lamps or equivalent devices, together with apparatus and circuitsV to accomplish the desired operation ofthe system.

Therapparatus for a singletrack switch at the feld station cornprises'aY switch machine con,

trol lever SML, a self-restoring starting button SB, a miniature track switch ts and a track ,occupancy indicating lamp OS. It will be under- 'stood thatVv one or more additional switch marchine leversmay be provided if a plurality Yof Vtrack switches are located at the iield station.

It will also ,be understood that one singlerstarting button SBVper station is used, irrespectivel of the number of control vlevers provided.

y jwSimilarly,` one or Vmore signal control leversV are provided.Y but forconvenience-onlya single signal control leverY SGL has been illustrated,

since the'contr'ol of the circuits by additional levers may readilyV be understood after anY explanation of the control by the illustrated levers,

fby way of example. vj

The control office includes a line relay F and a line repeating relay FP of the neutral quick acting type. A slow acting line repeating relay SA is controlled by relay FP to define the bounds of a cycle of operations, that is, relay SA is picked up at the beginning of a cycle, remains picked up throughout the cycle and is dropped after a predetermined period of time has been measured oli following the last impulse at the end of the cycle.

Associated with the line repeating relays is a bank of stepping relays including half-step relay VP and stepping relays IV, 2V, 3V and LV. This bank of stepping relays is for the purpose of marking off the successive steps of each cycle.

A starting relay STR starts the system into a cycle of operations in response to the initiation of a code call either from the control ofiice or from the eld station. Change relay CH2 is picked up in response to the actuation of button SB and this relay serves the purpose of initiating the system from the control oflice.

The S line circuit is energized with (-1-) or impulses from line battery LB in accordance with the operation of code sending relays PC and NC. More specifically, the S line circuit is energized with a (-1-) impulse when relay PC is picked up and with a impulse when relay NC is picked up. This polarity of energization is determined during the off periods and upon the picking up of the selected code sending relay PC or NC, the S line circuit is energized with the selected polarity. Y

Message receiving relays MA and MB of the biased to neutral polar type are connected in the A and B line circuits respectively and are for the purpose of receiving messages in the control oiiice in accordance with the indications being transmitted from the eld station.

Indication receiving relays IIR and 21R are provided to receive the indication which is transmitted from the eld station at the particular steps of the cycle, as selected by the operation of the stepping relay bank in the control oflice. These relays are of the polar magnetic stick type, that is, their contacts remain in the positions to which they were last actuated until shifted by the energization of their windings with an impulse of opposite polarity. Relay IIR receives the indication as to whether or not the track section at the field station is occupied and indicates this condition by energizing or de-energizing lamp OS. Relay 21R may receive any other indication required, but since the operation of relay IIR is typical of the operation of other indication receiving relays, the control of indicating devices by relay 21R is not shown. Resistance R is for the purpose of protection against short-crcuiting the battery in the event of an improper adjustment of the PC and NC relay contacts.

Field station equipment, preferred forma-The field station (see Fig. 3) comprises a turnout track connected to a main track by means of a track switch TS. This track switch is operated from one extreme locked position to the other by a suitable switch machine SM. The switch machine is controlled by a switch machine control relay SMR of the two-position polar magnetic stick type and this relay is governed from the control office through the medium of the communication system herein disclosed. Relay SMR controls the operation of the switch machine by energizing its normal or reverse operating wires from a local source of current as controlled by contact 40B. 'I'his control preferably includes suitable approach locking and other automatic signaling means as usually employed but not shown in the present disclosure for the sake of simplicity.

Suitable signals are associated with track switch TS for governing traiiic thereover. These signals are also governed from the control ofiice through the medium of the communication system in any suitable way by means of control relays such as relay SGR, operated from the control ofce in a similar manner as switch machine control relay SMR. The detailed circuit arrangement of the signal control at the field sta- I tion has been omitted from the present disclosure since it is immaterial for an understanding oi the present invention.

The detector track section has a normally closed track circuit with the usual track battery and track relay T for indicating the passage of trains.

The communication part of the system includes control line relay F1 of the quick acting, biasedto-neutral, polar type and resistance R1. The S line conductor is connected to the C line conductor in series with resistance R1 in order to provide the necessary drop in potential for energizing relays MA and MB during the transmission of indications. Quick acting relay FPl and slow acting relay SA1 are the line repeating relays at the station, similar to corresponding relays in the control ofce.

The eld station includes a bank ofY stepping w I relays, comprising half-step relay VP1 and stepping relays IVl, ZV1 and 3V1 which operate substantially in synchronism with corresponding relays in the control oice. rangement for operating this bank of stepping relays may be the same as that shown in detail for the control ofce bank of stepping relays, the detailed circuit arrangement has only been ndicated by the dotted line extending from front contact 428 of relay SA1 to the stepping relay bank.

A change relay CI-Il is provided toregister a change in condition of any of the traic controlling devices at the station so that the system will be initiated for the transmission of new indications. kThe detailed control of this relay has not been shown since it is well known in the art how such a relay is made responsive to a change in condition of traic controlling devices and resensitized during the succeeding cycle of opera.-

tions so that it may respondto the next change.

The A line impulse relay PLA and the B line impulse relay PLB are provided for selectively connecting the A and B lines respectively to the S and C lines as determined by the condition of the traffic controlling devices and these conditions are transmitted to the control oice by means or" indication codes made up by the selective operation of the PLA and PLB relays.

For the purpose of indicating how the different indication conditions are transmitted by the energization or the de-energization of relays PLA and PLB, relays M and T are provided. Relay M may be the usual signal indicating relay which is energized when all of the signals are at stop and de-energized when some one of the signals is in its proceed condition. Relay T is the track relay energized when the associated track section is unoccupied and (ie-energized when this track section is occupied.

Since the circuit ar- Operation of preferred form they follow each other at definite time intervals.

l29 cuits as determined by the positions of the con-Y control devices has taken placeYor not.

Y 35- has Vbeen actuated or not.

When a cycle is.'initiated for the transmission of.controls 'the character of the impulses placed upon the S line circuit is determined in accordance with the positions of the control levers in the control oiiice. During such a cycle, indications are-transmitted by means of the character of the impulses placed upon the A and IB line cirtrol devices at the Vfield station, as repeated by relays T and M for example.

When a cycle of operations is initiated from the control ofiice, a series of indications are Vtransmitted from the station to the oflice irrespective of whether a change in conditionV of the Like- Wise, when a cycle of operations is initiated from a iield station, the position of the contacts of the Vcontrol leversin'the oIice at that time are transmitted tothe fieldstation/irrespective ofVV Whether the starting button in the-control office It will thusV be seen that the ypresent Yinvention provides for the duplex operation ofY the system, that is, controls and indications are transmitted during a single -cycle'of operations. v

Normal conditions, preferred forms-Although Y the system may be initiated from the field station all line circuits are normally de-energized. In order to provide a means for initiating the system from the station the normally de-energized A line circuit is energized in response to the droppingr of change relay CI-Il. Relay CI-I1V is in its normally energized condition as previously mentioned and track relay T is normally energized when theV associated track section. is Vunoccupied. The remaining circuits of thesystern, bothy at the eld station and at the control oice,

are normally de-energized.

Manual start, preferred jarra- With the system in a condition of rest itis manually initiated into a cycle for the transmission of controls by the actuation ofY starting button SB after the control levers have been'suitably positioned.Y

For the purpose of considering the operation v of the present invention it will be assumed Vthat lever SMLY is in its right hand normal position and that lever SGL is in its center stop position. The actuation of button SB closes a circuit for picking up relay CH2 which extends from (-l-), contact 3|0 of button SB Vand windingrof relay` CH2 to Relay CH2 closes a stick circuit for itself extending from (V+), back contact' 3|| of relay SA, front contact 3|2 and winding of relay CH2, to

The picking up of relay CH2 closes a circuit for picking up relay STR which extends from back contact 3|3 of relay SA, back' contact 3|4 of relay LV, front contact73|8 of'relay CH2 and lower-winding of relay STR, to Relay STR The S line circuit is energized with potential because relay PC is now picked up over the circuit extending from back contacts 325, 326 and 321 of relays 3V, 2V and IV respectively, PCbus, winding ofrelayPC, front contact 328 of relay STR, back contacts329, 330, 33| and 332 of relays VP, |V, 2V and 3V respectively, to

The energizing circuit for the S line circuit ex.

tends from the terminal of battery LB, front contact 333 of relay PC, back contact 323 of relay NC, front contact 324 of. relay STR, winding of relay F, S line 'conductor 334, winding of relay F1, resistance R1, C line conductor 35, back contact 336 oi' relay NC and front contact 322 of relay PC, to the terminal of battery LB.

The circuit from battery LB (above traced) branches at the field station from S line conductor 331i where it 4maybe traced through front Contact (|22 of relay lSAl (picked up as later` described), Vback contacts 40| and m2Y of relays PLB and PLA respectively,'B line conductor 50 and A line conductor i0 in multiple, windings of and'MB are operated to their left hand dotted l relays MA and yMB to the center Vtap of battery LB. YCurrent flowing over this circuit is in such a direction that the polar contacts oi' relays MAV 'l positions and since polar contacts 54 and 62 of Y of relays MA andAMB connect to the channel selecting vcircuit arrangementoi the stepping Vrelays and since none of these relays are as yet operated, the actuation of these contacts is inelective at this time. Since polar contact 52 of relay MAris actuated to its left hand dotted position, this operation is vineffective to closetany" and relay FP closes an obvious circuit at its frontV contact 3BV for energizing relay SA. The opening of back Contact 3|| of relay SA de-energizes the stick circuit ofl relay CH2,fwhich allows this relay to drop.V V I ASterr-by-step' and' impulsirig operations of preferred jorm.-The energization of relay SA closes a circuit for picking up relay VP which extends from (-1-), I'ront contact 3|| of relay SA, front contact Mor relay FP, back contacts 42, 43 and 44 oi relays 3V, 2V and |VY respectively and Winding or relay VP, to Relay VP closes a first stick circuit for itself extending from (-i-),

' front contact 3|| of relay SA, front contact 5| of relay VP and over the remainder of the previously described circuit Y to the ywinding of relay VP.

The picking up of relay VP opens, at its back contact 329, the previously described energizing circuit for relay PC which allows this relay to drop for deenergizing the S line circuit at contacts 322 and 333.*This effects the dropping of relays F and FP in the office and relays Fl and FP1 at the field station. A second stick circuit is now completed for relay VP which extends from front contact 3II of relay SA, back contact 4lY of relay FP; front contact 45 and winding of relay VP, to

A pick up circuit for relay IV is now closed which extends from front contact 3I3 of relay SA, back contact 4B of relay FP, front contact 4l of relay VP, backcontact 3I6 of relay 2V and winding of relay IV, to Relay IV closes an obvious stick circuit for itself at its front contact 339.

Relay PC (or relay NCif selected by the control lever contacts) will now be picked up over a circuitv extending from back contacts 325 and 326 of relays 3V and 2V respectively, front contact 321 of relay IV, contacts of lever SML, winding of relay PC, front contact 328 of relay STR, front Contact 329 of relay VP, front contact 339 of relay IV, back contacts 33| and 332 of relays 2V and 3V respectively, to

The selected PC (or NC) relay energizes the S line circuit for again picking up relays F and FP, after which relay VP is de-energized because its rst stick circuit is open at back contact 44 of relay IV and its second stick circuit is open at back contact 4I of relay FP. The dropping oi relay VP de-energizes the selected PC (or NC) relay by reason of open front contact 329.

With both relays PC and NC (ie-energized the S line circuit is dre-energized, resulting in the dropping of relays F and FP to cause the picking up of relay 2V over a circuit extending from (-1-) front contact 3I3 of relay SA, back contact 43 of relay FP, back contact 4l of relay VP, back contact 355 of relay 3V, front contact 3I'I of relay IV and winding of relay 2V, to Relay 2V closes an obvious stick circuit for itself at its front contact 48.

The closure offront contacts 326 of relay 2V closes an energizing circuit for the PC or NC relay as selected by lever SGL. Upon the re sponse of the selected PC or NC relay the S line circuit is again energized and relays F and FP are picked up. Relay VP is now picked up over a circuit extending from front contact 3H of relay SA, front contact 4i of relay FP, back contact 42 of relay 3V, front contact 43 of relay 2V and winding of relay VP, to Relay VP again closes its iirst stick circuit which will be obvious from the circuit previously traced.

The picking up of relay VP opens the energizing circuit of the PC and NC relays so that the selected one of these relays is dropped to deenergize the S line circuit. This eiTects the dropping of relays F and FP so that a circuit is closed for picking up `relay 3V, extending from front contact 3I3 of relay SA, back Ycontact 43 of relay FP, front contact 4l of relay VP, front contact 3 i3 of relay 2V and winding of relay 3V, to Relay 3V closes an obvious stick circuit for itself at its front contact 49. The closure of back co-ntact 4I of relay FP again completes the second stick circuit for relay VP as previously described.

The picking up of relay 3V closes a circuit by Way oi its front contact 325 for energizing relay PC or relay NC (as selected by a control lever such as lever SGL). 'Ihis results in the energization of the S line circuit for picking up relays F and FP. Relay VP is now dropped because its rst stick circuit is open at back contact 42 of relay 3V and its second stick circuit is open at 'back contact 4Iy of relay FP.

The dropping of relay VP opens the energizing circuit of the selected PC or NC relay at open front contact 329 which results in both thel PC and NC relays being de-energized. This de-energizes the S line circuit forvdropping relays F and FP. A circuit is now closed for picking up relay LV which extends from front contact 3I3 of relay SA, back contact 46 of relay FP, back contact 41 of relay VP, front contact 3I5 of relay 3V and winding of relay LV, to

Since relay LV does not change the energizing circuit for the selected PC or NC relay, both of these relays remain cle-energized because the circuit extending to at front contact 332 of relay 3V is interrupted at front contact 329 of relay VP. This results in relays F and FP` remaining de-energized for a suiiiciently long period of time to release relay SA. The dropping of relay SA de-energizes the stick circuits of the stepping relays and starting relay STR at its front contact 3I3, with the result that these relays are dropped.

Since relay LV is slow acting, the (-I-) potential applied tothe stick circuit of relay STR is removed for a period of time suiiicient to allow this relay to drop its contacts and shortly thereafter relay LV closes its back contact 3| 9 for again energizing this stick circuit in preparation for the next cycle.

From the above description it will be understood that relays Fl and FP1 operate substantially in synchronism with relays F and FP and as above mentioned, the response of these line repeating relays at the l'ield station effects the operation of the stepping relay bank at the eld station in synchonism with the stepping relay bank in the control office. The stepping relays at the station are similarly de-energized when relay SA1 drops in response to the last long orf period of the stepping line circuit to ole-energize the stepping relay stickk circuit.

Polarity selection of control impulses, preferred O1'm-.-When the system is initiated from the control office as above described the rst (conditioning) impulse applied to the S line circuit is .in character by reason of the picking up oi relay PC. This application of energy to vthe S line circuit causes various relay operations which have already been described.

Assuming that the switch machine lever is in its right hand normal position as shown, the rst impulse applied tothe S line circuit (following the conditioning impulse) is as already described. In the event that lever SML is in its left hand dotted reverse position, relay NC is picked up over a circuit extending from back contacts 325 and 326 of relays 3V and 2V respectively, front contact 32'l of relay IV, contact of lever SML in its left hand dotted position, NC bus, Winding of relay NC, front contact 328 of relay STR, front contact 3290i relay VP, front contact 330 of relay lV, 'back contacts 33| and 332 of relays 2V and 3V respectively, to The energization of relay NC applies a impulse to the S line circuit.

This selection of the polarity of energization for the S line circuit occurs on each step by reason of the selection made at front contacts 321, 326 and 325 of relays IV, 2V and 3V respectively. This selection energizes relay PC or NC in accordance With the particular position of the control lever selected for each step. It will be understood that additional levers for other control purposes may be vprovided and selected through additional contacts of additional stepping relays when thesize of the system requires such extra selection.

From the above it will be seen Vthat the limpulse applied to the S line circuit during the conditioning period of a cycle initiated in the control oflice is (-1-), with thev following impulses applied to the S line circuit being (-1-) or in characterdependentV upon the positions Vof the control levers Yrendered effective by the stepping relays at the various steps of the cycle. This polarity determination is accomplished by two codesending relays-PC and NC whichare selectivelyenergized during the offperiods of the S line'circuit for controlling the succeeding on or energized periods with the proper polarities as selected. Y y

Transmission of controlamreferred form.- Upon the transmission of the first impulse (following. the conditioningimpulse) relay SMR at the field station is'energized for actuating'its polar contact 400 to the right or to the left depending upon the character of the impulse received.

With lever SML in its normal position as illus- `trated, the (-1-) impulse applied to the S line circuit actuates the contacts of relay F1 to the right. A circuit is now closed for actuating the contacts of relay SMR to the right extending from (B+), contact 405 of relay F1 in its right hand dotted position, back contacts 406 and 401 of V V'to the normal operating winding of switch machine SM for operating the track switch to its normal locked position.

' In the event that lever SML is in its left hand dotted (reverse) position, the impulse applied to the S line circuit actuates contact 405 of relay F1 to the left which applies (B to the circuit above described including relay'SMR. This positions contact 400 tothe left for applying energy to theV reverse operating winding. ofY switch Amachine SM which operates the track switch to its reverse locked position,

In a similar manner lever -SGL in its neutral position causes relay PC to 'be picked up for applying a (-1-) impulse to the S line circuit when Athe second step is taken. Thisy impulse actuates contact 405 of relay F1, to the right for applying (B-1-) to the winding of relay SGR over a circuit including front contact 401 of relay 2V1. It is believed unnecessary to show or explain the detailed operation of the circuits controlled by relay SGRVsince they form'no part of the present invention. J Y Y Field s'tartpreferred ,form. -This modification is ofY the codedY duplex type vand Vindications are transmitted from the station'to, the control oiiice during the same cycle thatcontrols Vare transmitted to the station. Y

' Referring to Fig. 3, a change in the condition of Y the detector track section or a change in the condition of other traffic devices at the station may occur at any time and for convenience in describingV the operation of this portion of the system it will .be assumed thatsuch change effects the de-energization' of relay CHI. The dropping of relay CI-I1 closes aV circuit for picking up relay PLA which extends from (-1-), back Contact 403 of .relay CHl',V Yback contacts Y404, |09 and 4I2 of relays IVl, 2V1and 3V1 respectively and winding of relay PLA, toy f l Y y The picking up of 'relay PLA closes a circuit for energizing the A line circuit which extends from the (-1-) terminal of the midtap of battery LB, winding of relay MA, A line conductor 40, front Contact 402 of relay PLA, C line conductor 35, back contact 32| of relay STR and back contact 322 Vof relay PC, tothe terminal of battery LB.

This energization of the A line circuit energizes relay MA and positions its polar contact 52 to the right which in turn closes a circuit for picking up relay STR extending from (-1-) back contact 3I3 of relay SA, back contact 3I4 of relay LV, contact 52 of relay MA in its right hand dotted position and lower winding of relay S'I'R, to VRelay STR closes the ypreviously described stick circuit for itself including its front contact 320 which maintains this relay energized until the end of the cycle. It will be noted that the picking up of relay STR opens the above described energizing circuit for relay MA, but before this relay has time to drop its contact 52 to its neutral position for de-energizing the lower winding of relay STR, the stick circuit including the upper winding of relay STR is completed.

The closure of front contact 324 of relay STR closes the circuit including the S line conductor and at front contact 328 the above described circuit for initially energizing relay PC is completed. The picking up of relay PC energizes the S line circuit with av (-1-) impulse as in the previously described control cycle and in response to this impulse relays VP and VP1 are energized. The picking up of relay VP opens-the circuit including relay PC and this relay drops to terminate the conditioning "on period. The system now steps through a cycle of operations as before. During the first off period (following the conditioning fon period) relay IV1 at the station is picked up to deenergize the above described circuit including relay PLA. The switching of contact 404 from its back to its front point therefore makes relay PLA dependent for its energization upon the circuit controlled by the device selectively governing the energization of the A Y and B line circuits.

circuit leading to (-1-) at back contact 4I3 of relay T is open so that relay PLA will not be picked up. When the control ofiice energizes the S line circuit witha (-1-) impulse for the next For example, with-track relay T energized when the first step is taken, the

(first) impulse period as previously described, the Y A line circuit is energized with a impulse overY a circuit extending from the (-1-) terminal of battery LB, front contact 333 of relay PC, back contact 323 of relay NC, front contact 324 of 'relay STR, winding of relay F, S line conductor 334, front contact 422 of relay SAl, back contact 402 of relay PLA, A line conductor 40 and winding of relay MA, to the mid-tap ofbattery LB. This positions the contacts of relay MA to their left hand dotted positions and a circuit is closed for energizing relay IIR and positioning its polar contact to its right hand position extending from (B+), resistance R, front contact 53 of relay PC,

contact 54 of relay MA in its left hand dotted position, back contacts 55 and 56 of relays 3V and 2V respectively, front contact 51 of relay IV and winding of relay IIR, to (CN): This positions contact 58 of relay IIR to the right Which maintains lamp OS de-energized as an indication that the track section is unoccupied.

In the event; that the impulse applied to the S line circuit is when this indication is trans-v mitted to the control office, relay NC Would be picked up and relay PC would be down. The A line circuit would then be energized over a circuit extending from the terminal of the midtap of battery LB, Winding of relay MA, A line conductor 45, back contact 402 of relay PLA, front contact 422 of relay SA1, S line conductor 334, winding of relay F, front contact 324 of relay STR, front contact 323 of relay NC and back contact 322 of relay PC, to the terminal of battery LB. Current flowing over this circuit energizes relay MA in the opposite sense and its polar contacts are positioned to the right. A circuit is now closed for energizing relay IIR with (B+) potential Which extends from (B+), resistance R, back contact 53 of relay PC, front contact 59 of relay NC, contact 54 of relay MA in its right hand dotted position and over the remainder of the previously described circuit to relay IIR. Contact 58 of relay IIR is in this instance again actuated to the right.

In the event that the track section is occupied, relay T is de-energized and its back contact 4I3 is closed. Relay PLA is picked up under this condition and (assuming the impulse applied to the S line circuit to be (I) a circuit is closed for energizing relay MA and actuating its polar contacts to the right which extends from the terminal of the midtap of battery LB, Winding of relay MA, A line conductor 40, front contact 402 of relay PLA, C line conductor 35, back contact 335 of relay NC and front contact 322 of relay PC, to the terminal of battery LB. In this instance (relay MA actuated to the right and relay PC picked up) relay IIR is energized with (B current for actuating its Contact 58 to its left hand dotted position, which closes an obvious circuit for energizing lamp OS to indicate that the track section is occupied. This circuit for relay IIR may be traced from (B front contact B5 of relay PC, contact 54 of relay MA in its right hand dotted position and over the previously described circuit to the Winding of relay IIR.

In the event that the S line circuit is energized with a impulse when this indication is to be transmitted, relay NC will be picked up and relay PC Will be down. Under this condition the A line circuit is energized with a impulse over a circuit extending from the (-I) terminal of battery LB, back contact 333 of relay PC, front contact 335 of relay NC, C line conductor 35. front contact 452 of relay PLA, A line conductor 40 and Winding of relay MA, to the midtap of battery LB. Relay IIR is energized from (B for positioning its contact 58 to its left hand dotted position over a circuit extending from (B back contact E!) of relay PC, front contact 6I of relay NC, contact 54 of relay MA in its left hand dotted position and over the previously described circuit to the Winding of relay IIR.

It will thus be seen that the channel circuits selected by the lower set of contacts on the stepping relay bank in the control oice are selectively energized in accordance With the energized or deenergized conditions of relay PLA at the field station. A selected channel circuit is energized in accordance with the position of polar contact 54 of relay MA in combination With the energized or deenergized condition of the code sending relays PC and NC, the latter energizing the S line circuit With impulses of positive and negative polarity respectively. In other Words, current for selectively actuating the MA relay is derived from the S line circuit irrespective of whether the S line circuit is energized with (I) or current, with a compensated arrangement effected by the PC or NC relay Which is picked up for energizing the selected channel circuit with the proper polarity, irrespective of the position to which relay MA is actuated.

The above typical example indicates how a selecticn of one ofV two indications is transmitted at a particular step of the cycle over the A line circuit and it will be understood that additional indications are transmitted in the same manner When additional channel circuits are selected by front contacts 40S` and 4I 2 of relays 2V1 and 3V1, respectively, at the station and received by Way of channel circuits in the oiiice selected by front contacts 56 and 55 of relaysV 2V and 3V respectively,

A choice of one of two additional indications is transmitted at each step by selectively energizing the B line circuit. For example, assuming that relay M is de-energized, then when the rst step is taken a circuit is closed for picking up relay PLB which extends from back contact I I4 of relay M, front contact I I 5 of relay IVI, back contacts II' and II'I of relays ZV1 and 3V1 respectively and Winding of relay PLB, to

During the next energized period of the S line circuit (assuming it to be (-I) the B line circuit is energized with (-I-) potential over a circuit extending from the (I) terminal of the midtap of battery LB, Winding of relay MB, B line conductor 5G, front contact 45| of relay PLB, C line conductor 35, back contact 336 of relay NC and front contact 322 of relay PC, to the terminal of battery LB.

Relay MB actuates its polar contact 62 to its right hand dotted position Which closes a circuit for energizing relay 21R extending from (B fro-nt contact 5I) of relay PC, contact 52 of relay MB in its right hand dotted position, back contacts G3 and 64 of relays 3V and 2V respectively, front contact 55 of relay IV and Winding of relay 21R, to (CN). Current flowing over this circuit actuates the polar contact of relay 21R to its left hand position.

In the event that the S line circuit is energized with a impulse when this indication is to be transmitted, then the B line circuit is energized with a; impulse for actuating polar Contact 62' of relay MB to its left hand dotted position over a circuit extending from the terminal of battery LB, back contact 333 of relay PC, front contact 335 of relay NC, C line conductor 35, front contact 43| of relay PLB, B line conductor 55 and Winding of relay MB, to the midtap of battery LB. Relay 21R is energized in the same direction as before over a circuit extending from (B back contact 5B of relay PC, front contact 5I of relay NC, contact 52 of relay MB in its left hand dotted position and over the previously described circuit to the Winding of relay 21R.

In the event that relay M is picked up, then relay PLB is de-energized during this iirst impulse and (assuming the S line circuit to be energized With a (-I) impulse), the B line circuit is energized With a impulse over a circuit extending from the terminal of battery LB, front contact 333 of relay PC, back contact 323 of relay NC, front contact 324 of relay STR, Winding of 75 relay F, S line conductor 334, front contact 422 of Yrelay SA1, back contact 40| Voi relay PLB, B line conductor 50 and Winding of relay MB, to themidtap of battery LB.

Relay vMB actuates polar contact 62 to its left handV dotted positionV for yclosing a circuit Which energizes relay 21R toits opposite position, which circuit extends from (B+), resistance R, front contact 530i relay PC, contact 52 of relay MB in its left hand'dotted position and over the previously described circuit to the Winding of relay Y In the event that the S line circuit is energized With a impulse when this indication is to be transmitted, the Bline circuit will be energized With'a impulse over a circuit extending from the Aterminal of the midtap of battery LB, Winding of relay MB, B line conductor 50, back Contact 40| of 'relay PLB, :front contact 422 of relay SA1, S line4V conductor 334, winding of relay F, front contact3r24 of relay STR, front contact 323 of relay NC and back contact 322 of relay PC,'to the terminal 'of battery LB. The ac-V tuation of contact 62 of relay MB to its right hand dotted .positionV closes `a circuit'for again energizing relay 21R with potential, which circuit extends from (B+), resistance R, back contact 53 of relay PC, front Contact 59 of relay NC, Vcontact S2 of relay MB in its right hand dotted position and over the remainder of the previously described circuit, to relay 21R.

' indicating to the operator the condition of relay M at the field station. V Although the transmis sion of a selection of any one of four indications has only been shown for the first step it will be understood that this arrangement may be employed for any number of steps desired by selecting a pair of channel circuits at each step by Way of front contacts of the stepping relays, such as contacts 409 and H6 for the second step and contacts 4l2 and Il'l for the third step.

During a cycle of operations for the transmission of indications, change relay CH1 at the station is restored to its picked up position in readiness for any other Vchange which may occur at thev eld station. The circuit arrangement for accomplishing this result is notshown since it is immaterial for an understanding of the present invention and since Various arrangements may be used for such accomplishment.

The restoration of the system to its normal condition at the endof an indication cycle effects the deenergization of the various relays in the same manner described in connection with a control cycle.

Duplex operation-+R has been pointed out that control and indication cycles are initiated from the control oiiice and the iield station respectively. YIt has also been mentioned that indications of the :existing conditions of the control devices at the station are transmitted to the oicre during the control cycle'and controls are transmitted from the office to the station in aecordance with the existing conditions of the control levers during an indication cycle. Therefore the resulting cycleof operationsY initiated from i the control olce or from the neld station results in two Way transmission, or in other Words, the duplex operation of the system.

Description. of modificatimil The modification shown in Figs. 4, 5 and 6 makes use of Vaiive Wire line circuit, over' which double the number of controls and indications (compared With theV system of Figs. 1, 2 and 3) are transmitted. The same fundamental principle used in the system already described, that is, the use of polar impulses derived from al source cf current in the control oflice for the transmis Ysion of indications, is used in this modification.

The schematic circuit diagram of Fig. 4 shows the five Wire line circuits and the apparatus most closely associated with these 'line circuits. The S line, in combination with the A and B Ylines forming return paths for impulses in the S line, is used for controlling the stepping operationand for ltransmitting a choice of two controls at each step. The A line, in .combination with the B line as a return conductor, is used for transmitting a choice of two additional controls for each step. As indicated in the control ofiice portion of this gure, line battery LB supplies energy for the transmission of stepping impulses and one set of controls, the polarity of which are determined!- by the PC and NC relays. The controls transimpulses from the source Vof current 2LB, withthe polarity determined by relay PX.

A choice vof fourindications is provided during the off periods by energizing the MA and MB line circuits With polar impulses selected at the iield station, the polarity of Which is supplied from battery 2LB in the control ofce connected to the A and B line conductors. These four off indications are selected through back contacts of relay FP1 at the eld station as indicated by the legends to other MAB (and to other MBB) indi` cation contacts as selected bythe stepping-relays. This refers to the fact that the MA and MB lines are conditioned through back contacts of relay FP1. The back contacts of relayFP in the control oce connect to relays MAB and MBB', which relays are operated by the polar impulses applied to the respective line circuits'.

vmitted over the A-B line circuit are made up of During the on periods, when relays FP and Control o17ce equipment, modification Referring to Fig.' 5, the apparatus in the con- Vtrol ofice consists of the same stepping relay bank as described in connection With the other modification and the same FP, SA, PC, NC and STR relays previously described. In this modiiica-`r tion, however, a line relay FS is included in the S line circuit and a. linerelay FA is included 'in the A line circuit. Furthermore, in place of the MA and MB relays of the previous arrangement, relays MAF, MAB, MBF and MBB are provided to receive theindication messages (double the number provided in the rst modification) from the iield station. Relay PX is provided for determining the Ypolarity with which the A-B line circuit'is energized. Relays E and EP are impulse relays controlled in response to the stepping relay operation for energizing and deenergizing the A-B line circuit at the proper times.

Field station equipment, modiyication included in the S line circuit and relay FA1 is included in the A line circuit. Resistance units |R1 and 2R1 are provided for connecting the S line conductor to the A and B line circuits, by means of which a drop in potential is provided for energizing the MA and MB line circuits during the transmission of indications.

In addition to the T and M relays at the field station, additional contacts 25S and 25| are provided for the purpose of indicating how a selection of two indications are transmitted over the MA line circuit and a selection of two indications are transmitted over the MB line circuit during the on periods or the periods When relay FP1 is: picked up. It will be understood that contacts 25B and 25| may be associated with any device from which it is desired to transmit indications.

Normal conditions, modification-The System is shown in Figs. 5 and 6 in its normal, at rest condition with the assumption that track relay T and change relay CHl are normally energized. Relay EP in the control oflice is normally energized over an obvious circuit through back contact |58 of relay E. The S line circuit, the MA line circuit and the MB line circuit are normally deenergized, but the A -B line circuit is normally energized over a circuit extending from the (1-) terminal of battery ZLB, back contact |5| of relay PX, front contact |53 of relay EP, winding of relay FA, A line conductor |65, winding of relay FA1, resistance |R1, resistance 2R1, B line conductor Il'll, front contact |54 of relay EP and back contact |55 of relay PX, to the terminal of battery 2LB.

Relays FA and FA1 are energized o-ver this circuit, relay FA closing its front contacts and relay FA1 closing its polar contact in a right-hand position.

M anual start, modification-The system of this modication is initiated from the control oice in the same Way as described in connection with the other mcdiication, that is, a change relay (such as relay CH2 of Fig. 2) is picked up in response to the actuation of the starting button, which in turn causes relay STR to be picked up and stuck up until the end of the cycle in the manner previously described.

The picking up of relay STR closes a circuit for picking up relay PC Which extends from (-1-), front contact |55 of relay FA, back contacts l5?, |58 and l 59 of relays 3V, 2V and IV respectively, front contact IBI of relay STR and winding of relay PC, to

The picking up of relay PC applies (-1-) potential tothe S line over a circuit extending from the (-1-) terminal of battery LB, back contact |62 of relay NC', front contact |53 of relay PC, Winding of relay FS, S line conductor |86, Winding of relay FS1, resistance |R1, Winding of relay FA1, A line conductor |5, Winding of relay FA, front contact |53 of relay EP, back contact i5! of relay PX, through the upper portion of battery 2LB, front contact 64 of relay PC and back contact |55 of relay NC, to the terminal of battery LB. The voltage of battery LB is suflicient to overbalance that of the oppositely poled upper portion of battery LB. Furthermore, at the point between resistances i R1 and 2R1 at the I'leld station this circuit branches and returns through resistance 2R1, B line conductor |70, front contact |54 of relay EP, back contact |55 of relay PX, through the lower portion of battery ZLB, front contact |64 of relay PC and back contact |65 of relay NC, to the terminal of battery LB.

Current flowing over this circuit energizes; the

S line with (-1-) potentialifor picking up relay FS and for positioning relay FS1 to the right. The response of relays FS and FS1 effect the picking up of relays FP, SA, FP1 and SA1 in the same manner described in connection with the previous modification. Furthermore, relays VP and VP1 are picked up during this conditioning on period in the same manner previously described and it is believed unnecessary to repeat the description of this operation. It will be noted that a stick circuit is provided for relay SA through iront contacts |56 of relay FA and |61 of relay SA. This is merely for the purpose of energizing the SA relay slightly in advance of its energization by relay FP, because relay FA picks up before relay FP at the beginning of each on period- Upon the response of relay VP a circuit is closed' for picking up relay E Which extends from (-1-) back contacts |58, |59 and l'll of relays 3V, 2V and lV respectively, front contact |12 of relay VP and Winding of relay E, to The opening of back contact |55 of relay E deenergizes relay EP .and after a comparatively long time interval, measured oit by its slow acting characteristics, relay EP opens its fro-nt contacts |53 and |55 for deenergizing the A-B line conductors. Since the return path for the S line conducto-1 includes the A and B line conductors the S line circuit is likewise dcenergized to mark the end or" the conditioning period.

Step-by-siep operation, modification- The step-by-step operations of the stepping relay banks in the control oflice and at the field station are controlled by relays FP and FP1 in the Inanner previously described in connection with the rst modification so that it is considered unnecessary to repeat this description. The line impulsing operation in the first modication was controlled by the stepping relays selecting the PC and NC relays direct. In the second modification the impulsing of the S line circuit is controlled by relays EP, PC and NC in combination. For example, the dropping of relay EP deenergizes the line circuits to mark the end of the conditioning period as just described. The deenergization of the A line circuit deenergizes relay FA which opens, at its iront contact |56, the circuit of the PC (or NC) relay, which in turn drops to maintain the S line circuit open, because the A-B line circuit will be energized before the S line circuit to start the next impulse period.

The picking up of relay lV during the first oil period opens the above described circuit of relay E and this relay drops to close the pick up circuit for relay EP. Upon the response of relay EP the A-B line circuit is energized as previously traced, resulting in the picking up of relay FA which closes at its iront contact |55 the circuit for energizing the next PC or NC relay for sending the next impulse out over the S line circuit.

it will thus be seen that the dropping of relay de-energizes the S line circuit by opening both the A and B line conductors and that when relay EP again picks up, the A and B line conductors are again energized but the S line conductor is not energized until the response-oi relays FA and PC (or NC).

Polarity selection` of control impulses, modification-When the system of this modification is initiated from the control oflice as above described the rst (conditioning) impulse applied to the S line circuit is (-1-) in character by reason of the picking up of relay PC. The A line circuit is nor- 15 mally energized with current of (-1-) character but during the conditioning impulse the positions of relays FS1 and FA1 at the field station are immaterial because the first channel circuit is not selected until during the deenergized or off period following the conditioning impulse.

Assuming that lever SML is in its normal position as shown inv Fig. 5, itwill be obvious that relay PC is picked up to apply a (-1-) impulse to the S line circuit on the second step because of the selection through front Contact |59 of relay |V just prior to this impulse period. In the event that lever SML is in its left-hand reverse position, relay NC is energized to apply a impulse to the S line circuit because of the reversed positions of the pole changing contacts on relays PC and NC.

This selection of thepolarity of energization for thel S line circuit occurs on each step by reason of'the selection madeat front contacts |59, |58 and |51 of relays IV, 2V and 3V respectively. This arrangement is in accordance With the previously described modication and it will be understood that' these polar impulses operate relay FS1 to the right or left for energizing (by means of contact |15) the control relays selected through contacts of the stepping relays, all in the same manner previously described'.

During the stepping operations at the control oflice and at the eld station the A-B line circuit is energized at each step from battery 2LB With a Ypolartity selected by relay PX. -For example, the iirst impulse (following the conditioning impulse) applied to the A line conductor is (-1-) in character because relay PX is deenergized due to the circuit selected Vthrough front contact |13 of relay |V leading to lever 3L, for example, which is in a position for disconnecting the (-1-) terminal of the'local battery source from the circuit leading to relay PX. With relay PX deenergized it is obvious that the (-1) terminal of battery 2LB is connected to the A line conductor and the terminal of this battery is connected to the B line conductor.

Assuming another control device, such as lever 4L, to be in the position indicated, then relay PX is energized over a circuit including front contact |14 of relay 2V so that the A line circuit is energized during the next impulse period with a impulse because of the reversed position of pole changing contacts |51 and |55 of relay PX. This transmission of polar impulses over the A line circuit actuates relay FA1 at the iield station to itsY right and Vleft hand positions for selectively energizing (by Vmeans of contact |85) additional channel circuits which may be lead to control relays, all of which is indicated by the bracket bearing the legend fTo control relays.

It is believed unnecessary to show or explain the detailed operation of the control relays connected to the channel circuits indicated, since this operation may be understood by referring to the operation of contact 405 of relay F1 of Fig. 3, remembering that contacts |15 -and |85 of relays FS1 and FA1 are selectively actuated in response to control impulses applied to the YS line and the A line circuits respectively.

alsa-iso station initiates the system.Y It Will then LbeY tion irrespective of Whether a'cycle of operations is initiated from the control oiiice or from the iield station.

Y Referring to Fig. 6, a change in the condition ofY a traiiic device at the station effects the deenergization of relay CH1 in a manner previouslyV described. The dropping oi relay CH1 closes ak circuit for energizing the MB line conductor Which circuit may be traced (recalling that the A line conductor is connected to the (,-1) terminal and the B line conductor is connected to the terminal of battery ZLB) from the (-1-) terminal oi the midtap of battery 2LB, Winding of relay MBB, back contact |16 of relay FP, back contact |11 of relay FS, MB line conductor |18, back contact |8| of relay FP1, back contacts |82, |83 and Ilrof relays 3V1, 2V1 and |V1 respectively, back contact of relay CHl, B line conductor |10, front contact |54 of relay EP and back contact |55 of relay PX, to the terminal of battery ELB. Current iiovvingY over this circuit actuates polar contact |52 of relay MBB to the right Which eiTects the energization of relay STR over a circuit not shown but Which is the same as controlled by polar contact 52 of relay MA of Fig. 2.

The picking up of relay STR closes the previously described circuit for energizing relay PC, which applies a, (-1-) impulse to the S line circuit as described in connection with a control cycle. Relays FS, FP, FS1 and FP1 are picked up as before and upon the response of relay FP1 the MB line conductor is de-energized at back contact 18|. This of course deenergizes relay MBB but polar Contact lill of this relay has not effected an IR relay operation because the iirst stepping relay has notyet responded.

When relay EP in they control oflice drops during this first (conditioning) impulse period the A-B line circuit is de-energized as before. This Y drops relays FA and FAl. Since the S line conductor has no return path to the battery in the control office, because of open front contactsV |53 and |511, the S line circuit is likewise deenergized. This drops relays FS and FS1 to mark the end o1 the conditioning on period. Relay PC is deenergized when relay FA opens its front contact |56.

It Will thus be seen that the system is initiatedfrom the field station by the momentary energization of line MB with a (-1-) impulse for positioning the contacts of relay MBB to the right,

mitted over the S line circuit and over theA-B line circuits.

Transmission of indications, modification- The indication circuits selected through back contacts IBI and |9| of relay FP.1 are conveniently referred to as 01T indications, since these indications are conditioned during the deenergized periods of the S line circuit, during Which periods relays FP and FP1 are down.

When relay EP in the control oflice picks up to close its fro-nt contacts |53 and |54 for energizing the A--B line circuit, the MA line conductor is energized With a (-1) polarity Vfor transmitting a rst choice OPindicatiorL The circuit for energizing line MA may be traced fromthe terminal of the midtap of battery 2LB, Winding of relay MAB, back contact |81 of relay FP, back contact |88 of relay FS, MA line conductor |19, back Contact |9| of relay FP1, back contacts 252 and 253 of relays 3V1 and ZV1 respectively, front contact 254 of relay |V1, front contact 255 of relay T, B line conductor |19, front contact |54 of relay EP and back contact |55 of relay PX, to the terminal of battery 2LB.

This actuates the contacts of relay MAB to their right-hand dotted positions, and assuming that relay PX is deenergized, a circuit is closed for energizing channel conductor |90, which circuit may be traced from (B+), resistance 5R., back contact |89 of relay PX, contact |92 of relay MAB in its righthand dotted position, back contacts |93 and |94 of relays 3V and 2V respectively and front contact |95 of relay IV, to conductor |99. It will be understood that conductor |99 may lead to an indication receiving relay such as relay IIR, of Fig. 2.

In the event that relay PX is picked up for transmitting a control over the A line circuit When this indication is to be transmitted, then relay MAB actuates its polar contacts to the left over the previously described circuit from the midtap o1" battery ZLB by way of the MA and the B line conductors, but in this instance through front contact l5! of relay PX, to the terminal of battery ZLB. With contact |92 in its left-hand dotted position channel conductor |99 is energized with potential over a circuit extending from (B+), resistance 5R, front contact |99 of relay PX, contact |92 of relay MAB in its left-hand dotted position and over the previously described circuit, to conductor |99.

In the event that track relay T is deenergized, then the circuit above described for energizing line MA extends through back contact 255 of relay T, over the A line conductor to the terminal of battery 21B (assuming relay PX down) by way of back contact |5| oi relay PX. This positions contact |92 of relay MAB to its left-hand dotted position and since relay PX is down, (B is connected to channel conductor |99 over a circuit extending from (B resistance 5R, back Contact |99 of relay PX, contact |92 of relay MAB in its left-hand dotted position and over the previously described circuit, to conductor |99.

In the event that relay PX is picked up when this indication is transmitted, relay MAB actuates its contact |92 to the: right because the previously described circuit extending from the midtap of battery ZLB through the Winding of relay MAB is connected to the A line circuit at back contact 255 of relay T and to the terminal of battery 2LB through front contact |55 of relay PX. Since relay PX is up and contact |92 of relay MAB is tothe right, (B is connected through front contact |39 of relay PX and contact |92 of relay MAB in its right-hand dotted position to channel conductor |99.

The above examples indicate how a choice of twol indications are transmitted over the MA line circuit for selectively energizing a channel circuit (|99) from the battery in the oilice which is reversibly connected to the A-B line circuit leading from the oilice to the: station. This choice of two indications derived from the central office battery selectively energizes. the selected channel circuit with one or another polarity, irrespectivey of the polarity with which the A-B line circuit is energized from the control oi'ce, even though the polarity for the indication is derived from this control oliice battery.

An additional choice of two indications are obtained when relays FP and FP1 are picked up by selectively energizing the MA line circuit. For example, when relay E in the control oiiice is picked up during the first impulse period the MA line conductor is energized over a circuit eX- tending from the midtap of battery 2LB, Winding of relay MAF, front contact |81 of relay FP, front contact |39 of relay FSI, front contact |98 of relay E, MA line conductor |19, iro-nt contact |9| oi relay FP1, back contacts 299 and 20| of relays 3V1 and 2V1 respectively, front contact 202 of relay |V1, back contact 250, A line conductor, Winding of relays FA1 and FA, front contact |59 of relay EP and back contact |5| of relay PX (assumed down) to the terminal of battery 2LB. This actuates polar contact |96 of relay MAF to the left and (B is connected to channel circuit |91 over a. circuit extending through resisto:I 6R, back contact |99 of relay PX, contact |95 of relay MAF in its left-hand dotted position and over an obvious channel selecting circuit to channel conductor |91. Y

In the event that relay PX is picked up when this indication is transmitted, then the circuit traced from the midtap of battery ZLB through the winding of relay MAF b-y Way of the A line conductor returns to the terminal of this battery through front contact |55 of relay PX. (B is in this instance applied to channel conductor |91 through front contact |89 of relay PX and through contact |96 of relay MAF in its righthand dotted position, because relay MAF is energized in an opposite sense from that previously described. Y

In the event that contact 259 is in its alternate position (and PX) down) for connecting with the B line conductor When this indication is transmitted, the circuit leading from the midtap of battery LB through the winding of relay MAF extends by way of front contact 25|) and the B line conductor to the terminal of battery ZLB because relay PX has its back contact |55 closed. This actuates contact |95 of relay MAF1 to the right and a (B+) potential is applied to conductor |91 through back contact |89 of relay PX and contact |99 of relay MAF in its righthand dotted position. In the event that relay PX is picked up when front Contact 25D is effective, then the circuit from the midtap of battery ZLB extends through the winding of relay MAF, iront contact 259, B line conductor and front Contact |5| oi relay PX to the terminal of battery ZLB. This actuates polar contact |95 of relay MAF to the left and in this instance (B+) potential is applied to conductor |91 through front contact |99 of relay PX and contact |99 of relay MAF in its left-hand dotted position.

The above examples indicate how a choice of two indications are transmitted over the MA line circuit during the picked up conditions of relays FP1 and FP. These two indications, plus the previously described choice of two indications efective when relays FP and FP1 are deenergized, provide a choice of four indications per step. It will now be explained how the MB line circuit is similarly conditioned for transmitting an additional choice oi four indications.

From the above it will be observed that the MA line is energized with a selected polar impulse Y by way of front contact |55 of relay PX.

Y of on indications.

between the picking up of relay EP and the picking up of relay FS for one group of 01T indications. It will' also be noted that the MA line is energized with a selected polar impulse between the picking up of relay E and the dropping of relay EP during the on period for one group It will now be explained how the MB line is energized with a selected polar impulse between the picking up of relay EP and the picking up of relay FS'for another group of off indications.V Also how the MB line is energized with aV selected polar impulse between the picking up of relay E and the dropping of relay EP for another group of on indications.

Assuming the iirst step to have been taken, that is, relays IV and IV1 picked up and that relays FP and FP1 are down, with contact 203 of relay M in the position shown the MB line circuit is energized with a impulse over a circuit extending from the midtap of battery 2LB, winding of relay MBB, back contact |16 of relay FP, back contact |11 of relay FS, MB line conductor |18, back contact 8| of relay FP1, back contacts |82 and |83 of relays 3V1 and 2V1 respectively, front contact |84 of relay |V1, back contact 203 of relay M, winding of relay FA1, A line conductor |60, winding of relay FA, front contact |53 of relay EP and back contact |5| of relay PX (assuming relay PX to be down) to the (-1-) terminal of battery ZLB. This actuates the polar contacts ofrelay MBB to their left-hand dotted positions and a circuit is closed for energizing channel conductor |40 with a polarity which circuit extends from (B-), resistance 6R, back contact |99 of relay PX, Contact 4| of relay MBB in its left-hand dotted position and over the channel selecting circuit of the stepping relays to con- In the event that relay PX is picked up when this Yindication is transmitted, the MB line conductor is energized with a (-1-) impulse over a circuit extending from the midtap of battery 2LB, winding of relay MBB and over-the previously described circuit, including A line conductor |60, to the terminal of battery ZLB In this instance conductor |40 is energized with potential over a circuit extending from (B-) resistance 6R, front contact |89 of relay PX, contact |4| of relay MBB in its right-hand dotted position (because of the (-1-) impulse applied to line MB) and over the remainder of the previously described circuit to conductor |40.

In the event that relay M is energized when this indication is transmitted (with relay PX down), the MB line conductor is energized with a (-1-) Aimpulse for positioning the contacts of relay MBB to their right-hand dotted positions. rThis circuit may be traced over the previously described circuit from the midtap of battery 2LB, including the winding of relay MBB (but this time through front contact 203 of relay M), to B line conductor |10 and thence to the terminal of battery 2LB by way of back contact |55 of relay PX. Channel conductor |40 is energized with a (-1-) potential under this condition over -a circuit extending from (B+), resistance 5R, back Contact |89 vof relay PX, contact |4| of relay MBB in its right-hand dotted position and over the channel selecting Vcircuit to conductor |40.

In the event that relay PX is picked up when this indication is transmitted, then the MB line conductor is energized With a impulse which is effective to position the contacts of relay MBB to their left-hand dotted positions over a circuit extending from the midtap of battery 2LB, winding of relay MBB, and over the previously described circuit including front Contact 203 .ofV relay M and B line conductor |10, to the (-1-) terminal of battery ZLB by way of front contact |51 Y of relay PX. Channel conductor |40 is energized with a (-1-) potential over a circuit extending from (B+), resistance 5R, front contact |99 of relay PX, contact |4| of relay MBB in its leftthe midtap of battery 2LB, winding of relay l MBF, front contact |16 of relay FP, front contacts |11 and |48 of relays FS and E respectively, MB line conductor |18, front contact |8| of relay FP1, back contacts |42 and |43 of relays 3V1 and 2V1 respectively, front contact |44 of relay |V1,

back contact winding of relay FA1, A line` conductor |60, winding of relay FA, front contact |53 of relay EP and back contact |5| of relay PX (assuming relay PX to be down), to the (-1-) terminal of battery 2LB. Y

This impulse over the MB line circuit actuates the polar contact of relay MBF to its lefthand dotted position for energizing channel conductor with a potential over a circuit extending from (B-), resistance 6R, back contact |99 of relay PX, contact |49 of relay MBF in its left-hand dotted position and overthe channel selecting circuit of the stepping relays to conductor |30. In the event that relay PX is picked up when this indication is transmitted,

' the MB line `conductor will be energized with a (-1-) impulse to position the polar contact of relay MBF to its right-hand dotted position, over a circuit extending from the midtap of battery 2LB, winding of relay MBF and over the previously described circuit including back contact 25| and A line conductor |60, to the terminal of battery 2LB by Way of front contact |55 of relay PX. Channel conductor |30 is energized with a potential under this condition over a circuit extending from (B-), resistance 6R, front contact |89 of relayPX, contact |49 of relay MBF in its right-hand dotted position and over the channel selecting circuit to conductor |30.

In the event that contact 25| is closed in its alternate position, 'then the indication transmitted a this point consists of a (-1-) impulse applied to the MB line conductor over a circuit extending from the midtap of battery 2LB, Winding of Vrelay MBF and over the previously described circuit including front contact 25| and B line conductor |10 to the terminal of battery 2LB, by way of back contact |55 of relay PX (assuming relay PX to be down). With polar contact |49 of relay MBF in its right-hand I dotted position and relay PX down, channel conductor |30 is energized with a (-1-) potential' this indication is transmitted the MB line conductor will be energized with a impulse to actuate polar contact |49 to its left-hand dotted position, over .a circuit extending from the midtap of battery 2LB, winding of relay MBF and over the previously described circuit including front contact 25| and B line conductor |70 to the terminal of battery 2LB, by Way of front contact of relay PX. Channel conductor |33 is `energized with (-1-) potential under this condition over a circuit extending from (B+), resistance 5R, front contact |99 of relay PX, contact |49 of relay MBF in its left-hand dotted position and over the channel selecting circuit to conductor |36.

It is believed that the above examples are sufficient t0 indicate how a choice of four indications per step is effective to energize fourchannel circuits such as conductors |90, |91, Illl and |34) each with one or another polarity as determined by the conditions of corresponding channel circuits at the field station. In other words, four out of eight indication conditions are selectively transmitted on each step of the cycle. It will be understood that other channel circuits selected at other steps of the cycle are likewise conditioned in the same manner.

Having thus described a centralized tramo controlling system as a preferred form and another and specic embodiments of the present invention, it is desired to be understood that these forms are selected to facilitate in the disclosure ratherthan to limit the number of forms which the invention may assume and it is further to be understood that various modifications, adaptations, and alterations may ber applied to the specic forms shown to meet the requirements of practice Without departing from the spirit of the invention except as limited by the appended claims.

What I claim is:

1. In a remote control system; a pair of control line conductors and an indication line conductor extending from a control oice to a distant eld station; devices at said station; means including a source of current in said omce for applying a series of time spaced control impulses to a line circuit including said control line conductors; control transmitting means in said ofce for reversibly connecting said source of current to said control line conductors, whereby said control impulses are marked with either of two polarities; means at said station selectively responsive to the polarity of said control impulses for selectively controlling said devices; indication transmitting means including a connection from an intermediate point of said source to said indication conductor at said ofce and contacts at said station for selectively connecting said indication line conductor in a circuit with either of said control line conductors and a portion of said battery, whereby distinctive indication impulses are transmitted to said oiiice; indication receiving means in said oilice responsive to said indication impulses; and compensating means controlled by said control transmitting means and said indication receiving means, whereby each distinctive indication impulse is identically registered irrespective of the polarity of energization of said control line conductors which effect the transmission of said indication impulses.

2. In a remote control system; a pair of control line conductors and an indication line conducto-r extending from a control olice to a distant eld station; governing devices at said station; means including a source of current in said-cnice for `applying a series. of time 4spaced control impulses to a control circuit including said control line conductors; control transmitting means in said office for reversibly connecting Ysaid source of current to said control circuit, whereby said control impulses are marked with either of two polarities; means at said station selectively responsive to the polarity ci said control impulses for selectively controlling said governing devices; indication transmitting means including a connection in said oice between said indication line conductor and an intermediate point lof said source and including contacts at said station for selectively connecting said indication line conductor in circuit with eitherv of said control line conductors concomitantly with the application of said control impulses and time spaces to said control line conductors, whereby distinctive indication impulses are transmitted to said oiilce of a polarity depending on both the polarity applied to said control circuit and on the particular control line conductor with which said indication line conductor was connected in` series; and indication receiving means in said oliice controlled so as to be responsive to said selective connection of said indication line conductor to said control line conductors irrespective of the polarity applied to the control line conductor during that particular impulse.'

3. In a remote control system; a pair of control line conductors and an indication line conductor extending from a control office to a distant field station; governing devices at said station; control transmitting means including a source of current in said oii'ice for applying a series of time spaced control impulses to a control circuit including said control line conductors; control transmitting means in said office for reversibly connecting said source of current to said control circuit, whereby said control impulses are marked with either of two polarities; means at said station selectively responsive to the polarity of said control impulses for selectively controlling said governing devices; means for connecting the oflice end of said indication line conductor to an v intermediate point of said source, indication transmitting means at said station for selectively connecting said indication line conductor to either of said control line conductors concomitantly with the application of said control ii-- pulses to said control line conductors to transmit distinctive indication impulses to said office over an indication circuit including said indication line conductor; indication receiving means in said onlce effective during the application of said control impulses responsive to said indication impulses; and compensating means controlled by said control transmitting means and said indication receiving means, for registering an indication character which is the source irrespective of the polarity of energization of said control line conductors which constituted the current source for the transmission of said indication impulses.

4. In a remote control system; a pair of control line conductors and a pair of indication line conductors extending from a control oflice to a distant eld station; governing devices at said station; means including a source of current in said office for applying a series of time spaced control impulses to 'said control line conductors; control transmitting means in said oilice for reversibly connecting said source of current to said control line conductors to constitute an ener- Vzo `line conducto-rs, whereby distinctive indication impulses are transmitted to said oice; indication receiving means in said oirlce selectively responsive to said.V indication impulses; and compen- Y sating means controlled by said control transmitting means and said indication receiving vmeans to deliver identically the same indication character irrespective of the polarity of energization of said control line conductors Which constituted the current source, for the transmission of said indication impulses. f

5, In a remote control system, a first and a Y second line wire extending from a control oflice Valso upon the condition of said indication con-K to a distant iield station, devices at said station, meansV including a source of current in said oflice for selectively applying positive or negative time spaced control impulses to a iirst line circuit including said rs't line Wire and a common wire,

manually operablemeans in said cnice for determining the positive or negative character of eachV control impulse, means at said station controlled in accordance with the character of said impulses for selectively controlling'said devices, indication devices in said oiiice, means including an automatically operable indication contact and a connection between said second line Wire and said source ofcurrent for selectively applying positive or negative time spaced indication impulsesto a second line circuit from either said rstline wire or said common Wire, said second circuit including said second line Wire of which the polarity of these impulses is 'dependent upon the polarity applied to said Yiirst line circuitV and tact,y electro-responsive means in said oflice seiectively controlled in accordance With the character of said indication impulses, and means in part controlled by said manually operable means for-interpreting said indication impulses by compensating for the polarity applied to said iirst line circuit. Y,

6. In a remote control system; a iirst, a second and a third line wire extending from a control oflice to a distant iield station; devices at Vand a common wire;

said station; means including a source of current in said oiiice for selectively `applying positive or negative time spaced control impulses toY a rst line circuit including said first line wire manually controllable means in said oice for determining the positive or negativecharacter of each control impulse applied to said first line circuit; means at said station controlled in accordance with the character of said control impulses for selectively controlling said devices; indication devices in said oiice; means including a connection between said second and third line Wires and said source of current and automatically operable meansat said stations for selectively Vapplying' positive or negative time spaced indication impulses derived from either .said first line wire or said common wire to a second line circuit including said secondY line Wire and a. third line circuit including said third line Wire; means including said manually and said automatically operable means `for determining theV positive or negative character of each indication impulse; and circuit means in said oflice selectively controlled in accordance with the character of said indicationyimpulses and the condition of said manually controllable means to compensate for the polarity of current applied to said rst line circuit.

'7. In a remote control system, a control 0fiice and a eld station connected by a control line circuit and an indication line circuit, means for applying impulses of current of positive and negative Vpolarity to said control line circuit, stepby-step mechanisms at said oflice and at said sta- Y tion operable in synchronism by said impulses irrespective of their polarity, a controlled device and a device to be indicated at said station, means responsive to the polarity of one of said impulses for selectively controlling Vsaid controlled device, means for applying an impulse to said indication line circuit from current derived from said'control line circuit and of a polarity dependent on both the polarity then existing'on the control line circuit and the condition Vof `the device to be indicated which device to be indicated mayV either connect the control line circuit directly or reversibly to the indication line Y circuit, and means responsive to the polarity of the impulse applied to said indication line circuit modied 'by the polarity applied to said controlv line circuit on the same step for indicating the condition of said device to be indicated. Y

8` In a remote control system,a :control 0f- Vrice and a eld station connected by a control line circuit and an indication line circuit, means for applying impulses of current of positive and Y negative polarity to characterize a code to said Y control line circuit, step-by-step mechanisms at said oilice and at said station operableA in synchronism by said impulses irrespective of their polarity, control devicesY at said iield station,

Yother Ydevices at'said station having indications to be transmitted, meansV responsive to the polarity of said impulses for selectively controlling i plied to said control line circuit on the same step for indicating the condition of said other devices. y

' NEIL D. PRESTON. 

